Systems and methods for quantifying and providing indicia of ST-segment resolution in an ECG signal

ABSTRACT

Systems and methods are provided for quantifying and providing indicia of ST-segment resolution in an electrocardiogram (ECG) signal. A receiver acquires an electrocardiogram (ECG) signal that includes an ST-segment. A processor processes the ECG signal to determine values for the ST-segment deviation relative to an isoelectric baseline. A user is allowed to provide a baseline signal to the processor. The processor responds to the baseline signal by marking a baseline ST-segment value corresponding to a baseline time. A user interface displays a linear graphical trend of variations in the measured ST-segment values relative to the baseline ST-segment value. In certain embodiments, the processor detects user-selected trigger events such as post-intervention ST deviation relative to the baseline time and the baseline ST-segment value, and provides indicia of the trigger event. In addition, or in other embodiments, a verbal annunciation of a percent ST-segment resolution is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/090,789, filed Aug. 21, 2008, which is incorporated herein byreference.

TECHNICAL FIELD

This disclosure generally relates to cardiac analysis.

SUMMARY

Systems and methods are provided for quantifying and providing indiciaof ST-segment resolution in an electrocardiogram (ECG) signal. In oneembodiment, a receiver acquires an ECG signal through a plurality ofleads. The ECG signal includes, for each of a plurality of detectedheart beats, an ST-segment between a QRS complex and a T wave. Aprocessor processes the ECG signal to determine values for theST-segment relative to an isoelectric value. One or more controlsprovide a user selected baseline signal to the processor. The processorresponds to the baseline signal by marking a baseline ST-segment valuecorresponding to a baseline time. A user interface in communication withthe processor displays a linear graphical trend of variations in themeasured ST-segment values relative to the baseline ST-segment value. Incertain embodiments, the processor detects a trigger event relative toat least one of the baseline time and the baseline ST-segment value, andprovides indicia of the trigger event. In addition, or in otherembodiments, a verbal annunciation of a percent ST-segment resolution isprovided.

Additional aspects and advantages will be apparent from the followingdetailed description of preferred embodiments, which proceeds withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically represents a typical ECG signal of a heart of anormal, healthy person and includes a P wave, a Q wave, an R wave, an Swave, and a T wave;

FIGS. 2A and 2B graphically represent respective ECG signals that differfrom the typical ECG signal shown in FIG. 1;

FIG. 3 is a simplified block diagram of a system for monitoringST-segment resolution according to one embodiment;

FIG. 4 graphically illustrates a user interface for displaying a lineargraphical trend of an ST-segment in a selected lead according to oneembodiment;

FIG. 5 graphically illustrates a user interface for displaying percentST-segment resolution values per ECG lead at predetermined or userselected times according to one embodiment;

FIG. 6 is a flow chart illustrating a method for dynamically monitoringST-segment resolution in a patient according to one embodiment;

FIG. 7A graphically represents using a selected post J-point time in anST-segment to evaluate ST-segment resolution according to oneembodiment;

FIG. 7B graphically represents using multiple post J-point times in anST-segment to evaluate ST-segment resolution according to anotherembodiment;

FIG. 8 is a flow chart illustrating a method for monitoring ST-segmentresolution in a patient according to one embodiment;

FIG. 9A graphically illustrates a user interface for displaying aplurality of overlapped ECG signals according to one embodiment;

FIG. 9B graphically illustrates a user interface that displays anenlarged version of a baseline ECG signal overlapping a current ECGsignal according to one embodiment;

FIG. 10 graphically illustrates a user menu interface usable with thesystem shown in FIG. 3 according to one embodiment;

FIG. 11 graphically illustrates a user menu for selecting a post J-pointvalue according to one embodiment;

FIG. 12 graphically illustrates a user menu for selecting STpresentation options according to one embodiment; and

FIG. 13 graphically illustrates a user menu for selecting groups ofleads for display according to one embodiment.

DETAILED DESCRIPTION

Electrical waves cause the heart muscle to pump. These waves passthrough the body and may be measured using electrodes attached to apatient's skin. Electrodes on different sides of the heart measure theactivity of different parts of the heart muscle. An electrocardiogram(ECG) displays voltages between pairs of electrodes (leads) fromdifferent directions. Thus, an ECG may be used to display an overallrhythm of the heart and weaknesses in different parts of the heartmuscle.

ECGs are used to measure and diagnose abnormal rhythms of the heart,including abnormal rhythms caused by damage to the conductive tissuethat carries electrical signals. The ECG may be measured using variouslead systems. Generally, the ECG is obtained by using a standard 12-leadarrangement, but it can be obtained by using other lead systemsincluding, for example, a 3-lead system.

When patients have myocardial ischemia or injury, an ST portion(discussed below) of the ECG signal in affected leads may deviate froman isoelectric line. The affected leads may indicate an ST elevationfrom the isoelectric line, and the reciprocal leads may indicate STdepression from the isoelectric line. Cardiologists quantify ST-segmentresolution in the affected leads to identify which patients with STelevation myocardial infarctions (STEMI) are at greater risk and mayneed more aggressive intervention.

In one embodiment disclosed herein, an automated method is used toquantify and display ST-segment resolution in affected ECG leads. Themethod provides for the automation and presentation of a user selectedbaseline ST-segment measurement, an elapsed time per ECG lead from thebaseline measurement to a user selected percentage of ST-segmentresolution (e.g., time to 20%, 30%, 50% and/or 70% ST-segmentresolution), and/or a percent ST-segment resolution per ECG lead at auser selected time (e.g., at 30, 60, 90, and/or 180 minutes) followingmeasurement of the selected baseline. The user (e.g., clinician) mayselect which of these measures to display. For example, the user mayselect to view an elapsed time to 50% ST-segment resolution on a lineargraphical trend, and/or the percentage ST-segment resolution at 60minutes.

In one embodiment, a method for dynamically monitoring ST-segmentresolution in a patient includes acquiring an ECG signal that includes,for each of a plurality of detected heart beats, an ST-segment between aQRS complex and a T wave. The method further includes, at a userselected time, determining a baseline value for the ST-segment relativeto an isoelectric value, measuring a plurality of ST-segment valuesrelative to the isoelectric value for a plurality of heart beats overtime, and displaying a linear graphical trend of variations in themeasured ST-segment values relative to the baseline value. In certainembodiments, the method also includes detecting a trigger event relativeto at least one of the user selected time and the baseline value, andproviding indicia of the trigger event.

In addition, or in another embodiment, an audible annunciation isprovided of percent ST-segment resolution from a baseline measurement.In a cardiac catheter laboratory (“cath lab”), for example,interventional cardiologists perform procedures such as coronaryangiography that generally require a focus on the instrumentation ofdevices in the heart. For example, the cardiologist or other clinicianmay perform intermittent fluoroscopic visualization of heart chambersand vessels. Thus, monitoring of the ECG and other vital signs may beperformed by other persons in the lab. The cardiologist, however, maydesire to be quickly informed about acute changes in ST-segments. Thus,this embodiment provides annunciation of percent ST-segment resolution(e.g., of one or more selected leads) from baseline measurements.

In one embodiment, a method for monitoring ST-segment resolution in apatient includes acquiring a plurality of ECG signals from respectiveleads attached to a patient, each ECG signal including an ST-segmentbetween a QRS complex and a T wave for each of a plurality of detectedheart beats. For each lead, the method also includes determining apercent ST-segment resolution as compared to respective baseline values.The method further includes comparing each of the percent ST-segmentresolutions to a threshold value, and (based on the comparison)providing a verbal annunciation of the percent ST-segment resolutionvalues that meet or exceed the threshold value. The verbal annunciationmay also include an identification of a corresponding lead for eachpercent ST-segment resolution value that meets or exceeds the thresholdvalue. In certain embodiments, for each respective lead, the methodincludes displaying an overlapping baseline ECG signal and a current ECGsignal. For each of the percent ST-segment resolution values that meetsor exceeds the threshold value based on the comparison, the method mayalso include highlighting (e.g., enlarging) the respective display ofthe overlapping baseline ECG signal and the current ECG signal.

The embodiments of the disclosure will be best understood by referenceto the drawings, wherein like elements are designated by like numeralsthroughout. In the following description, numerous specific details areprovided for a thorough understanding of the embodiments describedherein. However, those of skill in the art will recognize that one ormore of the specific details may be omitted, or other methods,components, or materials may be used. In some cases, operations are notshown or described in detail.

Furthermore, the described features, operations, or characteristics maybe combined in any suitable manner in one or more embodiments. It willalso be readily understood that the order of the steps or actions of themethods described in connection with the embodiments disclosed may bechanged as would be apparent to those skilled in the art. Thus, anyorder in the drawings or Detailed Description is for illustrativepurposes only and is not meant to imply a required order, unlessspecified to require an order.

Embodiments may include various steps, which may be embodied inmachine-executable instructions to be executed by a general-purpose orspecial-purpose computer (or other electronic device). Alternatively,the steps may be performed by hardware components that include specificlogic for performing the steps or by a combination of hardware,software, and/or firmware.

Embodiments may also be provided as a computer program product includinga machine-readable medium having stored thereon instructions that may beused to program a computer (or other electronic device) to performprocesses described herein. The machine-readable medium may include, butis not limited to, hard drives, floppy diskettes, optical disks,CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magnetic or opticalcards, solid-state memory devices, or other types ofmedia/machine-readable medium suitable for storing electronicinstructions.

FIG. 1 graphically represents a typical ECG signal 100 of a heart of anormal, healthy person and includes a P wave, a Q wave, an R wave, an Swave, and a T wave. The P wave represents atrial depolarization. Theinitial portion of the P wave is largely a reflection of right atrialdepolarization and the terminal portion is largely a reflection of leftatrial depolarization. When visible, the Q wave is any initial downwarddeflection after the P wave. The typical Q wave represents septaldepolarization. The R wave is the first upward deflection after the Pwave and represents early ventricular depolarization. The S wave is thefirst negative deflection after the R wave and represents lateventricular depolarization. The T wave is normally upright, somewhatrounded and slightly asymmetric. The T wave represents repolarization ofthe ventricles. A QRS complex 110 begins at the onset of the Q wave andends at the endpoint of the S wave. The QRS complex 110 represents theduration of ventricular depolarization.

Generally, little or no electrical activity is visible along anisoelectric line 112 during a PR-segment 114 and an ST-segment 116 ofthe ECG signal 100. The PR-segment 114 begins at an endpoint of the Pwave and ends at the onset of the QRS complex 110. The PR-segment 114represents the time it takes for an electrical impulse to reach theventricles from the A-V node. The ST-segment 116 begins at the endpointof the S wave and ends at the onset of the T wave. During the ST-segment116, the atrial cells are relaxed and the ventricles are contracted sothat electrical activity may not be visible. In other words, asindicated above, the ST-segment 116 is normally isoelectric.

FIGS. 2A and 2B graphically represent respective ECG signals 210, 212that differ from the “typical” ECG signal 100. As shown in FIGS. 2A and2B, the ST-segment 116 may experience elevation (FIG. 2A) or depression(FIG. 2B) from the isoelectric line 112 in a vertical direction.ST-segment elevation or depression may occur, for example, with cardiacinjury, ventricular aneurysms, Prinzmetals angina, pericarditis,myocardial ischemia, or other diseases. An artisan will recognize fromthe disclosure herein that ST elevation shown in FIG. 2A and the STdepression shown in FIG. 2B may occur in the same patient as detectedthrough different leads.

FIGS. 2A and 2B also illustrate locations of respective J-points 214.The J-point 214 is a junction between the QRS complex 110 and theST-segment 116. As discussed below, a selected time duration from theJ-point is used to determine a location where the amplitude of theST-segment is measured. For example, traditional ST-segment measurementsmay be made at approximately 1/16×R-R interval post J-point, where theR-R interval is the heart beat interval or distance between a selectedpoint on one ECG signal to the corresponding point on the succeedingsignal. This corresponds, for example, to a 60 msec post J-point time ata heart rate of approximately 60 beats per minute.

FIG. 3 is a simplified block diagram of a system 300 for monitoringST-segment resolution according to one embodiment. The system 300includes a plurality of leads 310 electrically connected to a receivercomponent 312 that is in communication with a processor 313, a memorydevice 314, a display device 316, an audio component 318, and aninterface component 320. The leads 310 include wires and electrodesconfigured to attach to a patient (not shown) to detect ECG signals. Thereceiver 312 may include, for example, an amplification component 322 toamplify the ECG signals detected by the leads 310, a filtering component324 to eliminate undesirable noise from the ECG signals, and ananalog-to-digital (A/D) converter 326 to provide converted ECG signalsthrough a system bus 328 to the processor 313.

The processor 313 may include a special purpose processor configured toperform the processes described herein. In another embodiment, theprocessor 313 is a general purpose processor configured to executecomputer executable instructions (e.g., stored in the memory device 314)to perform the processes described herein. In addition, or in otherembodiments, the processor 313 may be connected to a host computer 330having a display device 332. The host computer 330 may include computerexecutable instructions for performing the processes described herein.The host computer 330 may be used in certain embodiments, for example,to provide remote patient monitoring.

In one embodiment, the system 300 allows a clinician to select one ormore indicators of myocardial reflow for use in guiding a patient'stherapy. The system then automatically monitors and displays theselected indicators on at least one of the display devices 316, 332. Incertain embodiments, the audio component 318 provides an audible alarmand/or verbal annunciation of ST-segment resolution percentages thatexceed a defined threshold. The interface component 320 may include, forexample, an integrated keypad, touch screen, or other user controls. Theinterface component 320 may also include, for example, interfaces for anexternal keyboard, a mouse, a printer, an external storage device,and/or a network adapter.

In one embodiment, a clinician may press a key, for example, to manuallymark the ST-segments (from available ECG leads) as baselinemeasurements. The clinician may also mark the ST-segments at theinitiation of an intervention and enter text that describes the marker(e.g. “baseline” or “thrombolytic”). The system 300 monitors the patientand automatically displays the clinician selected indicators ofST-segment change in the ECG leads that meet predefined or selectedmeasurement criteria.

FIG. 4 graphically illustrates a user interface 400 for displaying alinear graphical trend of an ST-segment in a selected lead according toone embodiment. The user interface 400 may be displayed, for example, onthe system display device 316 and/or the host display device 332 shownin FIG. 3. The user interface 400 graphically displays a baseline value410 of the ST-segment relative to the ST trend 412, which corresponds tovariations in the ST-segment over time. Thus, the user may quicklycompare the historical ST-segment value with the baseline ST-segmentvalue.

As shown in FIG. 4, the ST trend 412 may be plotted relative to timedisplayed in an x-axis 414. The time displayed in the x-axis 414 may bean actual time of day (e.g. 11:15:00, 11:30:00, 11:45:00 . . . ) on adisplayed date 416 or an elapsed time relative to measuring the baselinevalue 410 and/or treating the patient. The ST trend 412 may also beplotted relative to a measured voltage value displayed in a y-axis 418.Thus, using the values displayed in the x-axis 414 and the y-axis 418,the user may quickly determine the numerical value of the ST-segment ata selected point in time. The user may also quickly determine apercentage of ST-segment resolution.

In one embodiment, the user interface 400 automatically displays one ormore markers that indicate a time to reach a trigger event such as apredetermined or user selected ST-segment resolution threshold. Forexample, the user interface 400 may display markers relative to the STtrend 412 to indicate when 20%, 30%, 50%, and/or 70% ST-segmentresolution is reached for the selected lead.

In the example shown in FIG. 4, a first marker 420 corresponds to anintervention and includes an arrow at the time of the intervention, adisplayed time of day when the intervention was administered to thepatient, and user entered text to indicate the type of intervention(e.g. a “thrombolytic” was administered at 11:15:00). A second marker422 corresponds to the trigger event and includes an arrow at the timeof the trigger event, a time of the trigger event and text describingthe trigger event (e.g., 50% ST-segment resolution was reached at12:08:00). Thus, the user is visually notified that the time to 50%ST-segment resolution for lead II is 53 minutes. In certain embodiments,the audio component 318 provides an audible alarm (e.g., a tone orverbal announcement, as discussed below) when a trigger event isdetected.

Although a single trigger event marker 422 (50% ST-segment resolution)is displayed in FIG. 4, an artisan will recognize from the disclosureherein that multiple trigger event markers may also be displayed (e.g.,for 20%, 30%, 50%, and/or 70% ST-segment resolution). Further, multiplelinear graphical trends 412 corresponding to various affected leads maybe displayed together. An artisan will also recognize from thedisclosure herein that other types of markers and/or information mayalso be displayed including, for example, an elapsed time betweenmeasuring the baseline value and administering the intervention, anelapsed time between measuring the baseline value and the second marker422, an elapsed time between the first marker 420 and the second marker422, shapes other than arrows, the ST-segment value and/or percent ofST-segment resolution at the time of the first marker 420, and colors todistinguish between various markers.

FIG. 5 graphically illustrates a user interface 500 for displayingpercent ST-segment resolution values per ECG lead at predetermined oruser selected times according to one embodiment. The user interface 500may be displayed, for example, on the system display device 316 and/orthe host display device 332 shown in FIG. 3. In certain embodiments, theuser interface 500 may be displayed in addition to the user interface400 shown in FIG. 4.

The predetermined or user selected times displayed in the user interface500 may be relative to the baseline measurement time and/or theintervention time. Thus, the user may quickly determine quantitativevalues for affected leads at various times. In the example shown in FIG.5, numeric percentage values for ST-segment resolution are provided forlead II, lead III, and lead AVF at 30 minutes, 60 minutes, 90 minutes,and 180 minutes. An artisan will recognize from the disclosure hereinthat any lead may be selected for display of its percent ST-segmentresolution.

FIG. 6 is a flow chart illustrating a method 600 for dynamicallymonitoring ST-segment resolution in a patient according to oneembodiment. The method 600 includes acquiring 610 an ECG signal andreceiving 612 user selected criteria for evaluating ST-segmentresolution. As discussed in detail below with respect to FIGS. 7A and7B, the criteria for evaluating the ST-segment resolution may include auser selected post J-point time at which the system 300 measuressuccessive ST-segment values, or defining parameters for using multiplepost J-point times to statistically analyze ST-segment changes (e.g., bydetermining variance, skew, kurtosis, and/or other characteristics ofdata points measured within the ST-segment). The criteria for evaluatingST-segment resolution may also include display options, alarm options,and trigger event options. The system may include a set of defaultcriteria for evaluating the ST-segment. The user may also be allowed todefine one or more of the default criteria.

The method 600 also includes receiving 614 a baseline initiation signal,measuring 616 a baseline ST-segment value according to the selectedcriteria in response to the baseline initiation signal, and displaying618 indicia of the baseline ST-segment value. In one embodiment, thebaseline initiation signal is activated when the ECG signal is firstdetected and the criteria for evaluating the ST-segment resolution areknown. In addition, or in other embodiments, the baseline initiationsignal is set by the user to reset the baseline at a desired time (e.g.,at a time corresponding to a treatment administered to the patient). Atime at which the baseline ST-segment value is measured may be referredto herein as a “baseline time.” As shown in FIG. 4, the indicia of thebaseline ST-segment value may include a horizontal line 412 and/or amarker 420.

The method 600 includes periodically measuring 620 the ST-segmentdeviation according to the selected criteria and displaying 622 a lineargraphical trend of variations in the ST-segment deviation relative tothe baseline ST-segment value. The ST-segment values may be measured,for example, every heartbeat (e.g., every detected J-point 214), aselected fraction of the heartbeats (e.g., every fourth detected J-point214), or at selected or predetermined intervals (e.g., approximatelyevery 90 msec). As discussed above, an example linear graphical trend412 of variations in the ST-segment relative to the baseline ST-segmentvalue 410 is shown in FIG. 4.

The method 600 may also include detecting 624 a trigger event relativeto the baseline time and/or value and providing 626 indicia of thetrigger event. As discussed above, the trigger event may includedetecting a selected or predetermined percentage of ST-segmentresolution (e.g., upon detecting 20%, 30%, 50%, and/or 70% ST-segmentresolution). The trigger event may also correspond to a selected orpredetermined time after the baseline time (e.g., 30 minutes, 60minutes, 90 minutes, and/or 180 minutes after the baseline time).

The method 600 shown in FIG. 6 may be used, for example, when a patientis in a hospital's emergency department with chest pain, being monitoredin a coronary care unit while receiving intravenous fibrinolytics orother interventions, in a telemetry unit being monitored via a wirelesstransmitter to a central station monitor, or during a catheterizationprocedure in the catheterization lab. Busy healthcare providers mayforget to measure and calculate the ST-segment changes at appropriatetimes. Further, there may be different levels of expertise wherein notall personnel are trained to make ST-segment resolution measurements.Thus, an automated technique such as the method 600 shown in FIG. 6advantageously standardizes and systematically implements a protocol inan emergency department, coronary care unit, or other treatmentfacility. Such a method provides selected, institutionally acceptedmeasurements that automatically appear on the patient's monitor and/orcentral station when a trigger event is detected, indicating a selectedmagnitude of ST-segment resolution. This data may be accessible at anytime on the patient's monitor and/or the central monitoring system.

FIG. 7A graphically represents the use of a selected post J-point timet_(ST) in an ST-segment 116 to evaluate ST-segment resolution accordingto one embodiment. For illustrative purposes a baseline ECG signal 710(dashed line) is shown overlapping a current ECG signal 712 (solid line)with the peak values of the respective R waves aligned. In oneembodiment, known techniques are used to automatically determine andtrack the J-point time t_(J) of the respective ECG signals 710, 712. Auser may select a post J-point time t_(ST) (e.g., 20 msec, 40 msec, 60msec, 80 msec) at which a height difference Δy_(ST) between the baselineECG signal 710 and the current ECG signal 712 is determined. Acardiologist or other skilled health care provider may select the postJ-point time t_(ST) based on factors such as the patient's heart rate.

Selection of the post J-point time t_(ST) may have a drastic affect onthe ST-segment resolution value. For example, if the post J-point timet_(ST) were selected such that it were in an area 714 closer to the Twave, the change in height Δy_(ST) between the baseline ECG signal 710and the current ECG signal 712 would be much less than that shown inFIG. 7A. In other words, not every point within the ST-segment 116 willlikely reach a selected ST-segment resolution (e.g., 50%) at the sametime. Thus, in certain embodiments, multiple post J-point times are usedto evaluate ST-segment resolution.

For example, FIG. 7B graphically represents using multiple post J-pointtimes in an ST-segment 116 to evaluate ST-segment resolution accordingto another embodiment. In this example, ST-segment values are measuredat multiple post J-point times beginning with an initial time t₀ and afinal time t₁. The distance between post J-point times is represented bydt. An artisan will recognize from the disclosure herein that any numberof post J-point times within the ST-segment 116 may be used, and may belimited in certain embodiments only by the speed at which the datapoints may be measured. Between the initial time t₀ and the final timet₁, the difference between the baseline ECG signal 710 and the currentECG signal 712 varies between Δy₀ and Δy₁.

Various techniques may be used to evaluate changes in measured data setscorresponding to the baseline ECG signal 710 and the current ECG signal712. For example, integration techniques may be used to determine thearea between the baseline ECG signal 710 and the current ECG signal 712during the interval from the initial time t₀ and the final time t₁. Inanother embodiment, a trigger may be detected when any of the measuredpoints between the initial time t₀ and the final time t₁ reaches aselected threshold value (e.g., 50% resolution).

In addition, or in another embodiment, various statistical techniquesmay be used such as comparing the mean value or standard deviation ofthe baseline data set to the mean value or standard deviation of thecurrent data set. Another statistical technique may include comparingthe variance or distribution spread of the data sets about theirrespective mean values by calculating the second moment of therespective data sets. In addition, or in another embodiment, the skew orlack of symmetry may be compared by calculating the third moment of therespective data sets. In addition, or in another embodiment, thekurtosis or degree to which the distribution is peaked may be comparedby calculating the fourth moment of the respective data sets. An artisanwill recognize from the disclosure herein that many other knownstatistical techniques may be used to evaluate changes to the ST-segment116 over time.

In certain embodiments, audible alarms and/or other audible indicationsare automatically provided when a threshold ST-segment resolution valueis reached on one or more leads. For example, in one embodiment, verbalannunciation of percent ST-segment resolution of one or more selectedleads is provided when a user selected percent ST-segment resolution isdetected. For example, if the user selects notification when theST-segment percent resolution is greater than or equal to 20%, thesystem 300 shown in FIG. 3 may announce, “33% ST-segment resolution inLead V1 and 25% ST-segment resolution in Lead V2.”

In addition to the annunciated quantitative ST changes, a visualcomparison of the baseline ECG signals to current ECG signals isprovided in certain such embodiments for some or all of the ECG leads.In some embodiments, ECG signals with ST-segment resolutions that reachthe threshold, or ECG signals corresponding to selected leads, areautomatically magnified or otherwise highlighted on the user interface.The user interface may display one baseline ECG signal (e.g.,corresponding to a pre-intervention heart beat) using a first line color(or pattern) for each affected lead, superimposed with the current ECGsignal of the same respective lead in a second line color (or pattern).Together with the quantitative ST-segment resolution, the visual ECGchanges may be part of an ST report provided to the user.

FIG. 8 is a flow chart illustrating a method 800 for monitoringST-segment resolution in a patient according to one embodiment. Themethod 800 shown in FIG. 8 includes acquiring 810 a plurality of ECGsignals corresponding to selected leads, receiving 812 user selectedcriteria ST-segment resolution, receiving 814 a baseline initiationsignal measuring 816 baseline ST-segment values for each selected lead,and periodically measuring 818 ST-segments for each selected leadaccording to the selected criteria.

For each selected lead, the method 800 further includes comparing 820 acurrent ST-segment value to the corresponding baseline value andquerying 822 whether the ST-segment resolution for the lead has reacheda threshold value. If none of the leads has reached the thresholdST-segment resolution value, the method 800 continues measuring 818ST-segment for each selected lead and comparing 820 the current STsegment value to its corresponding baseline value. Once one or moreleads reach the threshold ST-segment resolution value, the method 800provides a verbal annunciation of percent ST-segment resolution perselected lead. In one embodiment, the annunciation (e.g., “50%ST-segment resolution in lead II”) is provided for all selected leads.In another embodiment, the annunciation is only provided for leads thathave reached the threshold value.

As shown in FIG. 8, in some embodiments the method 800 also includes,for each selected lead, displaying 826 an overlap of the baseline ECGsignal and the current ECG signal. For example, FIG. 9A graphicallyillustrates a user interface 900 for displaying a plurality ofoverlapped ECG signals 910 (twelve overlapped pairs shown) according toone embodiment. In this example, current ECG signals are displayed assolid lines overlapped with their respective baseline ECG signals asdashed lines, for each lead (lead I, lead II, lead III, lead aVR, leadaVL, lead aVF, lead V1, lead V2, lead V3, lead V4, lead V5, and leadV6). The R wave of each current ECG signal is aligned with the R wave ofits corresponding baseline ECG signal. In certain embodiments, differentcolors may be used for current ECG signals and baseline ECG signals.

While FIG. 9A shows overlapped ECG signals 910 for each lead in atwelve-lead system, in certain embodiments a user may select a subset ofleads to display. As shown in FIG. 9A, the user interface 900 mayinclude other information such as a current date 912, a current time914, selected criteria for measuring ST-segments (e.g., measuring eachST-segment at a post J-point time of approximately 60 ms), and a currentheart rate 918. An artisan will recognize that the user interface 900may also display other information such as a baseline ST-segment valueper lead, a current ST-segment value per lead, and/or a percentST-segment resolution per lead.

The method 800 may also include highlighting 828 displayed ECG signalscorresponding to ST-segment resolutions that have reached the threshold.For example, in addition to (or instead of) displaying the userinterface 900 shown in FIG. 9A, the method 800 may display an enlargedversion of overlapped ECG signals 910 corresponding to leads withST-segment resolutions that have reached the threshold. For example,FIG. 9B graphically illustrates a user interface 920 that displays anenlarged version of a baseline ECG signal 922 (dashed line) overlappinga current ECG signal 924 corresponding to a particular lead (e.g., leadI) that has reached an ST-segment resolution threshold according to oneembodiment. The user interface 920 may display the location of theisoelectric line 112, a location 926 (e.g., selected post J-point value)where the ST-segment is measured, the percent ST-segment resolution 928(e.g., 50%), an elapsed time 930 between the baseline ECG signal 922 andthe current ECG signal 924 (e.g., 53 minutes), and an indication 932 ofthe corresponding lead (e.g., lead I).

The method 800 shown in FIG. 8 may be used, for example, in acutesituations when users (e.g., clinicians) are performing procedures andhave other concurrent tasks that may not allow the user to view andcalculate ST-segment changes from the ECG waveform data.

FIG. 10 graphically illustrates a user interface menu 1000 usable withthe system 300 shown in FIG. 3 according to one embodiment. The userselectable functions discussed below with respect to the user interfacemenu 1000 may include software menu items (e.g., selectable with amouse), dedicated controls (e.g., front panel controls), keystrokes on akeyboard, and/or other user interactions.

The user interface menu 1000 allows a user to select a “set baseline”function 1010 to reset the ST-segment baseline for available ECG vectors(leads). When the user activates the set baseline function 1010,selected ECG waveforms and corresponding ST-segment numeric data arebookmarked for later comparisons. In one embodiment, bookmarkingincludes recording the selected waveforms for a predetermined amount oftime. For example, in one embodiment, selecting the set baselinefunction 101 records the selected ECG waveforms and correspondingST-segment values for a minimum approximately six seconds. An artisanwill understand from the disclosure herein, however, that much shorteror much longer times may also be used.

The user interface menu 1000 also allows the user to select a “relearnbaseline” function 1012 that causes the current ECG complex from eachavailable lead to become the most recently learned baseline morphology.The ST-segment values from each ECG lead (e.g., deviations from theisoelectric line) become the baseline numeric values and the point fromwhich high and low alarm limits trigger the ST alarm annunciation.

In one embodiment, the user interface menu 1000 also allows the user toselect an “ST-segment measurement criteria” function 1014. As discussedabove, the user may specify when each ST-segment measurement is to becarried out and/or define statistical measurements for evaluatingST-segment resolution. In one embodiment, the system 300 is configuredto dynamically analyze ST-segment deviation with variations in heartrate. Using known algorithms, the system 300 provides accurateST-segment measurements without constant user surveillance to repositionthe isoelectric line, J-point value, and/or post-J point value. Thealgorithms are also used to automatically measure ST-segment values bydetermining the vertical distance from the isoelectric line to the postJ-point measurement location.

In addition, or in other embodiments, the user may select the postJ-point value from a menu. For example, FIG. 11 graphically illustratesa user menu 1100 for selecting a post J-point value according to oneembodiment. The user menu 1100 allows a user to select, for example, a20 msec, 30 msec, 40 msec, 60 msec, or 80 msec post J-point value. Theuser menu 1100 also allows the user to make a “custom selection” toenter a desired post J-point value that is not listed in the menu. Incertain embodiments, the system 300 automatically places a post J-pointcursor at the selected time for measuring ST-segments, until such timeas the user may change the post J-point duration. In one embodiment, thesystem 300 provides a warning to the user when the ECG complex does notallow sufficiently accurate ST-segment measurements when relatively longpost J-point durations are selected (e.g., when a high heart rate causesthe selected post J-point to be located proximate to or within the Twave).

In addition, or in other embodiments, the ST-segment measurementcriteria function 1014 may allow the user to select from variousstatistical analysis options for multiple data points acquired withinthe ST-segments. For example, as discussed above, the user may selectcomparisons based on variance, skew, kurtosis, or other statisticalanalysis functions. The user may also be allowed to define parameters touse in the statistical analysis such as start and stop times within theST-segment, and distances between acquired data points.

In one embodiment, the user interface menu 1000 allows the user toselect a “freeze” function 1016 to hold the display of a current ECGsignal. In certain such embodiments, the user is allowed to positionelectronic cursors or calipers on the display screen to manually measurethe ST-segment elevation or depression.

In one embodiment, the user interface menu 1000 allows the user toselect an “ST presentation options” function 1018 that provides the userwith the ability to select from a variety of two-beat superimpositionoptions. For example, FIG. 12 graphically illustrates a user menu 1200for selecting ST presentation options according to one embodiment. Theoptions include displaying baseline ST values to current ST values,displaying baseline ST values to peak deviations, displaying baseline STvalues to selected ST alarm events, displaying peak ST values to currentST values, displaying peak ST values to post-intervention ST values,displaying baseline ST values to 60 minutes post-intervention ST values,and displaying baseline ST values to 90 minutes post-intervention STvalues. An artisan will recognize from the disclosure herein that otherdisplay options my also be available. In one embodiment, a defaultpresentation includes displaying baseline ST values to current STvalues.

Returning to FIG. 10, the user interface menu 1000 may also allow a userto select an “ST alarms” function 1020 that provides the user with theability to select a percent ST-segment resolution threshold and/or apost-intervention time. When ST alarm limits are violated in oneembodiment, for example, the user is able to quickly compare thebaseline ST values to those leads which violated alarm limits, asdiscussed above in relation to FIGS. 9A and 9B.

The user interface menu 1000 may also allow a user to select a “markevent” function 1022 that provides the user with the ability to mark anevent (bookmark) to indicate a time corresponding to an intervention(treatment) or patient symptom. As discussed above, the intervention maybe labeled on available waveform data and trend data to correspond tothe time of the marked event. The user is able to compare the baselineECG values to the time at which an event was marked.

The user interface menu 1000 may also allow a user to select a “displayleads” function 1024 that provides the user with the ability to groupand display specific ECG leads (e.g., from a list of available leads forthree, five, six, and ten-lead wire systems) per myocardial segmentanatomy such as anterior, posterior, inferior, and lateral ventricularwalls. For example, FIG. 13 graphically illustrates a user menu 1300 forselecting groups of leads for display according to one embodiment. Inthis example embodiment, grouped leads that may be selected for displaycorrespond to inferior ischemia (leads I, II, and AVF), lateral ischemia(leads I, AVL, V5, and V6), septal ischemia (leads V1 and V2), posteriorischemia (leads V1, V2, and V3), and global ischemia (leads AVF, V2, andV6). The user interface also includes a “custom selection” option toselectively group any combination of leads for display.

It will be understood by those having skill in the art that many changesmay be made to the details of the above-described embodiments withoutdeparting from the underlying principles of the invention. The scope ofthe present invention should, therefore, be determined only by thefollowing claims.

1. A system for dynamically monitoring ST-segment resolution in a patient, the system comprising: a receiver to acquire an electrocardiogram (ECG) signal through a plurality of leads, the ECG signal including, for each of a plurality of detected heart beats, an ST-segment between a QRS complex and a T wave; a processor to process the ECG signal to determine values for the ST-segment relative to an isoelectric value; one or more controls to provide a user selected baseline signal to the processor, the processor responding to the baseline signal by marking a baseline ST-segment value corresponding to a baseline time; wherein the one or more controls further allow the user to select criteria for evaluating ST-segment resolution, wherein the processor determines the values for the ST-segment based on the user selected criteria, and wherein the user-selected criteria further comprises one or more statistical algorithms selected from the group comprising mean, standard deviation, variance, skew, and kurtosis; and a user interface in communication with the processor to display a linear graphical trend of variations in the measured ST-segment values relative to the baseline ST-segment value.
 2. The system of claim 1, wherein the processor is further configured to: detect a trigger event relative to at least one of the baseline time and the baseline ST-segment value; and provide indicia of the trigger event.
 3. The system of claim 2, wherein the trigger event comprises an ST-segment resolution percentage reaching a threshold value.
 4. The system of claim 3, wherein the indicia of the trigger event comprises a marker displayed at a location on the linear graphical trend corresponding to an elapsed time when the ST-segment resolution percentage reaches the threshold, wherein the marker indicates the elapsed time and the ST-segment resolution percentage.
 5. The system of claim 3, further comprising an audio component to provide an audible signal for the indicia of the trigger event.
 6. The system of claim 5, wherein the audible signal comprises a verbal annunciation that communicates the ST-segment resolution percentage.
 7. The system of claim 6, wherein the verbal annunciation further communicates an identification of a lead that acquired the ECG signal.
 8. The system of claim 2, wherein the trigger event comprises a lapse of a predetermined amount of time after a user-selected time.
 9. The system of claim 8, wherein the indicia of the trigger event comprises a display of a measured percentage ST-segment resolution value on the user interface for one or more leads relative to the lapsed time.
 10. A system for dynamically monitoring ST-segment resolution in a patient, the system comprising: a receiver to acquire an electrocardiogram (ECG) signal through a plurality of leads, the ECG signal including, for each of a plurality of detected heart beats, an ST-segment between a QRS complex and a T wave; a processor to process the ECG signal to determine values for the ST-segment relative to an isoelectric value; one or more controls to provide a user selected baseline signal to the processor, the processor responding to the baseline signal by marking a baseline ST-segment value corresponding to a baseline time; wherein the one or more controls further allow the user to select criteria for evaluating ST-segment resolution, wherein the processor determines the values for the ST-segment based on the user -selected criteria, wherein the user-selected criteria comprise a post J-point value at which the processor determines the values for the ST-segment; and a user interface in communication with the processor to display a linear graphical trend of variations in the measured ST-segment values relative to the baseline ST-segment value.
 11. A system for dynamically monitoring ST-segment resolution in a patient, the system comprising: a receiver to acquire an electrocardiogram (ECG) signal through a plurality of leads, the ECG signal including, for each of a plurality of detected heart beats, an ST-segment between a QRS complex and a T wave; a processor to process the ECG signal to determine values for the ST-segment relative to an isoelectric value; one or more controls to provide a user selected baseline signal to the processor, the processor responding to the baseline signal by marking a baseline ST-segment value corresponding to a baseline time; wherein the one or more controls further allow the user to select criteria for evaluating ST-segment resolution, wherein the processor determines the values for the ST-segment based on the user-selected criteria, and wherein the user-selected criteria comprise selection of multiple post J-point values; and a user interface in communication with the processor to display a linear graphical trend of variations in the measured ST-segment values relative to the baseline ST-segment value.
 12. A system for dynamically monitoring ST-segment resolution in a patient, the system comprising: a receiver to acquire an electrocardiogram (ECG) signal through a plurality of leads, the ECG signal including, for each of a plurality of detected heart beats, an ST-segment between a QRS complex and a T wave; a processor to process the ECG signal to determine values for the ST-segment relative to an isoelectric value; one or more controls to provide a user selected baseline signal to the processor, the processor responding to the baseline signal by marking a baseline ST-segment value corresponding to a baseline time; and a user interface in communication with the processor to display a linear graphical trend of variations in the measured ST-segment values relative to the baseline ST-segment value; wherein the processor is further configured to: detect a trigger event relative to at least one of the baseline time and the baseline ST-segment value, wherein the trigger event comprises an ST-segment resolution percentage reaching a threshold value; and provide indicia of the trigger event, wherein the indicia of the trigger event comprises a marker displayed at a location on the linear graphical trend corresponding to an elapsed time when the ST-segment resolution percentage reaches the threshold, wherein the marker indicates the elapsed time and the ST-segment resolution percentage.
 13. A system for dynamically monitoring ST-segment resolution in a patient, the system comprising: a receiver to acquire an electrocardiogram (ECG) signal through a plurality of leads, the ECG signal including, for each of a plurality of detected heart beats, an ST-segment between a QRS complex and a T wave; a processor to process the ECG signal to determine values for the ST-segment relative to an isoelectric value; one or more controls to provide a user selected baseline signal to the processor, the processor responding to the baseline signal by marking a baseline ST-segment value corresponding to a baseline time; and a user interface in communication with the processor to display a linear graphical trend of variations in the measured ST-segment values relative to the baseline ST-segment value; wherein the processor is further configured to: detect a trigger event relative to at least one of the baseline time and the baseline ST-segment value, wherein the trigger event comprises an ST-segment resolution percentage reaching a threshold value; and provide indicia of the trigger event, wherein the system further comprises an audio component to provide an audible signal for the indicia of the trigger event, and wherein the audible signal comprises a verbal annunciation that communicates the ST-segment resolution percentage.
 14. The system of claim 13, wherein the verbal annunciation further communicates an identification of a lead that acquired the ECG signal. 